What is 2+2-(5-6) also can you tell me does a tree make a sound when it falls

Which functions are even? check all of the boxes that apply. f(x) = x4 – x? f(x) = x2 – 3x + 2 f(x) = (x - 2) f(x) = x done

Determine the mean and variance of the random variable with the following probability mass function. f(x)=( 729divided by 91) (1 divided by 9) superscript x baseline comma x equals 1,2,3 round your answers to three decimal places (e.g. 98.765).

Researchers were interested in whether relaxation training decreases the number of headaches a person experiences. they randomly assigned 20 participants to a control group or a relaxation training group and noted the change in number of headaches each group reported from the week before training to the week after training. which statistical analysis should be performed to answer the researchers' question?